Demonstration of electroluminescent TPC technology for neutrinoless double beta searches using the NEXT-DEMO detector

La tesis comença amb la descripció del camp de la física de neutríns i la seva evolució en els últims anys. Els primers capitols proporcionen una descripció detallada de la motivació teórica de la naturalessa Majorana del neutrí, les seves implicacions i quins son els processos mès suceptibles de ser medits experimentalment. En este sentit explica perquè la desintegració doble es el process on hi ha mès possibilitats de trobar processos que violen el nombre leptonic en dos unitats i per tant es un dels processos on s’està fent un esforç mès gran en aconseguir resultats experimentals. A continuació fa una explicació i un resum dels experiments actuals mès importants, principalment EXO-200, KamLand-Zen i GERDA, explicant amb detall tant el process experimental com els resultats obtessos. En el següent capitol fa una descripció del detector NEXT. En primer lloc es descriu el process de detecció dels senyals en el detector on s’introdueix el concepte “Separated Optimized Function TPC” (SOFT). Concepte que es fonamental per conseguir un detector que siga capaç d’obtenir una reconstrucció topológica dels events dins del detector sense renunciar a la excellent resolució en energia que tan sols es pot aconseguir en detectors de gas amb una amplificació lineal com la que aconseguim amb el process de l’electroluminescencia. Aquest process, el de l’electroluminescencia, també ve descrit en aquest capitol resaltant els concepts mès importants i perquè es tan important per a un detector com el que la colaboració NEXT vol construïr. A continuació, es passa a la descripció del detector NEXT-DEMO que es sobre el que s’ha realitzat el treball de la tesis. La descripció d’aquest detector inclou tot tipus de detalls, desde el tipus de materials emprats fins a la descripció del trigger per a l’adquisició de dades passant per els camps electrics als que operava el detector o la pressió a la que ho feïa. Tot seguit, es present els primers resultats que es varen obtindre amb aquest detector i que son la part fonamental de la tesis. Aquest resultats impliquen resolució d’energia i reconstrucció de la posició i la topologia dels events amb dos configuracions diferents: Amb un plà de tracking format per 19 tubs fotomultiplicadors (PMTs), i una segona configuració amb fotomultiplicadors de Silici (SiPMs). Al llarg d’aquests capitols s’explica el process d’anàlisis de la senyal. En aquest sentit, es descriu quines son les dificultats per a conseguir una bona resolució en energia (correció degut a la perduda de electrons al llarg de la deriva en el detector, correccions espacials relacionades amb les diferents eficiencies dels fotomultiplicadors,…) i s’explica com solucionar estes dificultats per a aconseguir una de les millors resolucions en energía del món per a aquests tipus de detectors. Pel que fa a la reconstrucció topológica, es descriu el proces basic de reconstrucció emprant el mètode del baricentre i es mostra la reconstrucció d’alguns events dins del detector NEXT-DEMO. Per últim, la tesis finalitza en capitol on es descriuen els dos següents detectors que la col·laboració està construïnt: NEW i NEXT-100. En aquest capitol es fa una descripció dels materials i el disseny d’aquestos dos detectors. Per a concluïr, es mostra quina es la sensitivitat sobre la vida mitja del process de desintegració doble beta que esperem obtindre amb NEXT-100

Bicolour fluorescent molecular sensor for cations: design and experimental validation

Molecular entities whose fluorescence spectra are different when they bind metal cations are termed bicolour fluorescent molecular sensors. The basic design criteria of this kind of compound are presented and the different fluorescent responses are discussed in terms of their chemical behaviour and electronic features. These latter elements include intramolecular charge transfer (ICT), formation of intramolecular and intermolecular excimer/exciplex complexes and Fo ̈rster resonance energy transfer (FRET). Changes in the electronic properties of the fluorophore based on the decoupling between its constitutive units upon metal binding are also discussed. The possibility of generating fluorescent bicolour indicators that can capture metal cations in the gas phase and at solid–gas interfaces is also discussedThis work was supported by the Basque Government (Grants IT-1346-19 and IT1180-19), by the Spanish Ministry of Science and Innovation (MICINN-FEDER, Grants PID2019-104772GB-I00, PID2019-111281GB-I00, RED2018-102387-T, and RED2018-102471-T), and by the European Research Council (ERC) under the European's Union Horizon 2020 research and innovation programme (Grant agreement ERC-2020-SyG 951281)

High Pressure Gas Xenon TPCs for Double Beta Decay Searches

This article reviews the application of high pressure gaseous xenon time projection chambers to neutrinoless double beta decay experiments. First, the fundamentals of the technology and the historical development of the field are discussed. Then, the state of the art is presented, including the prospects for the next generation of experiments with masses in the ton scale range

The electronics of the energy plane of the NEXT-White detector

[EN] This paper describes the electronics of NEXT-White (NEW) detector PMT plane, a high pressure xenon TPC with electroluminescent amplification (HPXe-EL) currently operating at the Laboratorio Subterraneo de Canfranc (LSC) in Huesca, Spain. In NEXT-White the energy of the event is measured by a plane of photomultipliers (PMTs) located behind a transparent cathode. The PMTs are Hamamatsu R11410-10 chosen due to their low radioactivity. The electronics have been designed and implemented to fulfill strict requirements: an overall energy resolution below 1% and a radiopurity budget of 20 mBq unit(-1) in the chain of Bi-214. All the components and materials have been carefully screened to assure a low radioactivity level and at the same time meet the required front-end electronics specifications. In order to reduce low frequency noise effects and enhance detector safety a grounded cathode connection has been used for the PMTs. This implies an AC-coupled readout and baseline variations in the PMT signals. A detailed description of the electronics and a novel approach based on a digital baseline restoration to obtain a linear response and handle AC coupling effects is presented. The final PMT channel design has been characterized with linearity better than 0.4% and noise below 0.4mV.We acknowledge support from the following agencies and institutions: the European Research Council (ERC), Spain under the Advanced Grant 339787-NEXT; the Ministerio de Economia y Competitividad of Spain under grants FIS2014-53371-C04, the Severo Ochoa Program, Spain SEV-2014-0398 and the Maria de Maetzu Program, Spain MDM-2016-0692; the GVA of Spain under grants PROMETEO/2016/120 and SEJI/2017/011; the Portuguese FCT and FEDER, Spain through the program COMPETE, projects PTDC/FIS-NUC/2525/2014 and UID/FIS/04559/2013; the U.S. Department of Energy under contracts number DE-AC02-07CH11359 (Fermi National Accelerator Laboratory), DE-FG02-13ER42020 (Texas A&M) and de-sc0017721 (University of Texas at Arlington); and the University of Texas at Arlington. We acknowledge partial support from the European Union Horizon 2020 research and innovation programme, Spain under the Marie Sklodowska-Curie grant agreements No. 690575 and 674896. We also warmly acknowledge the Laboratorio Nazionale di Gran Sasso (LNGS) and the Dark Side collaboration for their help with TPB coating of various parts of the NEXT-White TPC. Finally, we are grateful to the Laboratorio Subterraneo de Canfranc for hosting and supporting the NEXT experiment.Álvarez-Puerta, V.; Herrero Bosch, V.; Esteve Bosch, R.; Laing, A.; Rodriguez-Samaniego, J.; Querol-Segura, M.; Monrabal, F.... (2019). The electronics of the energy plane of the NEXT-White detector. Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment. 917:68-76. https://doi.org/10.1016/j.nima.2018.11.126S687691

The Event Detection System in the NEXT-White Detector

[EN] This article describes the event detection system of the NEXT-White detector, a 5 kg high pressure xenon TPC with electroluminescent amplification, located in the Laboratorio Subterráneo de Canfranc (LSC), Spain. The detector is based on a plane of photomultipliers (PMTs) for energy measurements and a silicon photomultiplier (SiPM) tracking plane for offline topological event filtering. The event detection system, based on the SRS-ATCA data acquisition system developed in the framework of the CERN RD51 collaboration, has been designed to detect multiple events based on online PMT signal energy measurements and a coincidence-detection algorithm. Implemented on FPGA, the system has been successfully running and evolving during NEXT-White operation. The event detection system brings some relevant and new functionalities in the field. A distributed double event processor has been implemented to detect simultaneously two different types of events thus allowing simultaneous calibration and physics runs. This special feature provides constant monitoring of the detector conditions, being especially relevant to the lifetime and geometrical map computations which are needed to correct high-energy physics events. Other features, like primary scintillation event rejection, or a double buffer associated with the type of event being searched, help reduce the unnecessary data throughput thus minimizing dead time and improving trigger efficiency.The NEXT collaboration acknowledges support from the following agencies and institutions: the European Research Council (ERC) under the Advanced Grant 339787-NEXT, the Ministerio de Economia y Competitividad and the Ministerio de Ciencia, Innovacion y Universidades of Spain under grants FIS2014-53371-C04, RTI2018-095979, the Severo Ochoa Program SEV-2014-0398 and the Maria de Maetzu Program MDM-2016-0692; the GVA of Spain under grants PROMETEO/2016/120 and SEJI/2017/011; the Portuguese FCT under project PTDC/FISNUC/2525/2014, under project UID/FIS/04559/2013 to fund the activities of LIBPhys, and under grants PD/BD/105921/2014, SFRH/BPD/109180/2015 and SFRH/BPD/76842/2011; the U.S. Department of Energy under contracts number DE-AC02-06CH11357 (Argonne National Laboratory), DE-AC02-07CH11359 (Fermi National Accelerator Laboratory), DE-FG02-13ER42020 (Texas A&M) and DE-SC0019223/DE-SC0019054 (University of Texas at Arlington); and the University of Texas at Arlington. DGD acknowledges Ramon y Cajal program (Spain) under contract number RYC2015-18820. We also warmly acknowledge the Laboratori Nazionali del Gran Sasso (LNGS) and the Dark Side collaboration for their help with TPB coating of various parts of the NEXT-White TPC. Finally, we are grateful to the Laboratorio Subterraneo de Canfranc for hosting and supporting the NEXT experiment.Esteve Bosch, R.; Toledo Alarcón, JF.; Herrero Bosch, V.; Simón Estévez, A.; Monrabal Capilla, F.; Álvarez-Puerta, V.; Rodriguez-Samaniego, J.... (2021). The Event Detection System in the NEXT-White Detector. Sensors. 21(2):1-19. https://doi.org/10.3390/s21020673S11921

Monocolor chemosensors for Ba2+ tagging experiments

Resumen del póster presentado a la XXXVIII Reunión Bienal de la Real Sociedad Española de Química, celebrada en el Palacio de Congresos de Granada, del 27 de junio al 30 de junio de 2022.The BOLD experiment is focused on the observation of the neutrinoless double β decay of 136Xe to 136Ba2+ through the detection of the daughter cation. For this purpose, different molecular sensors can be developed. These chemosensors can be classified into monocolor (offon) or bicolor (on-on’), depending on the shifts (Δλ) and changes in the intensity (ΔI) observed in their emission spectra. In this context, different off-on radiometric chemosensors have been synthesized in order to understand their photophysics upon interaction with Ba2+ ions in vacuo and in solution. These sensors incorporate two components: a fluorophore and a metal-binding group. The fluorophores are kept as simple as possible, using structures with well-known photophysical properties. On the other hand, N-aza-crown ether derivatives have been used as metal-binding groups. Finally, the effects of disconnecting the abovementioned elements by splitting of components Ar1 and Ar2 (Figure 1: Description of the off-on chemosensors synthesized in this work), will be discussed.Financial support from the Basque Government (IT-1346-19 and IT-1180-19), the Spanish MICINN (PID2019-104772-GB-I00, PID2019-111281-GB-I00, RED2018-102387-T, and RED2018-102471-T), and by the European Commission (ERC-2020-SyG-951281) is gratefully acknowledged.Peer reviewe

New generation of fluorescent bicolour sensors for barium tagging experiments

Resumen del póster presentado a la XXXVIII Reunión Bienal de la Real Sociedad Española de Química, celebrada en el Palacio de Congresos de Granada, del 27 de junio al 30 de junio de 2022.One of the most important questions in particle physics and cosmology consists of demonstrating that the neutrino is a Majorana fermion. Observation of the neutrinoless double β decay of 136Xe to generate the daughter cation 136Ba2+ is the most promising practical way to demonstrate this hypothesis. Within this context, our research group has designed and synthesized the first generation of fluorescent bicolour sensors (FBI-G1), whose emission spectra change upon binding to Ba2+ ions by formation of supramolecular complexes in dry media involving solid-gas interphases. In this presentation, the synthesis of a second generation (G2) of bicolour sensors is reported. These sensors have two essential components, a metal-binding group, and a fluorophore. The latest structure is based on a benzo[a]imidazo[2,1,5-cd]indolizine derivative (Figure 1: Description of generation 1 (left) and generation 2 (right) chemosensors). Finally, preliminary research involving the linkage of our sensors to surfaces such as indium tin oxide glass (ITO), will be discussed.Financial support from the Basque Government (IT-1346-19 and IT-1180-19), the Spanish MICINN (PID2019-104772-GB-I00, PID2019-111281-GB-I00, RED2018-102387-T, and RED2018-102471-T), and by the European Commission (ERC-2020-SyG-951281) is gratefully acknowledged.Peer reviewe

Iridium-based sensor for cations

Resumen del póster presentado a la XXXVIII Reunión Bienal de la Real Sociedad Española de Química, celebrada en el Palacio de Congresos de Granada, del 27 de junio al 30 de junio de 2022.Traditionally, techniques such as inductively coupled plasma mass spectroscopy or gas chromatography have been used for cation detection. However, these methods need long analysis times and sophisticated instrumentation. Simpler and faster methods have been developed these days, such us optical methods (colorimetric and/or fluorescent), which can entail easy visualization, high sensitivity and cheaper instrumentation. Among these, ratiometric (bicolour) fluorescent sensors stand out due to the lower limit of detection. In this area, both organic molecules and metal complexes are being developed as luminescent probes. Indeed, some iridium complexes demonstrated to be selective luminescent sensors for different cations. Different strategies are used to trap or interact with the cation, which permits a rational tuning of the iridium’s emission. In our group, we have been working with iridium complexes for a variety of objectives. In this contribution, an iridium-based sensor for cations will be described including its response to cations in solution and on solid supports.Financial support from the Basque Government (PRE_2020_2_0230, IT-1346-19 and IT-1180-19), the Spanish MICINN (PID2019-104772-GB-I00, PID2019-111281-GB-I00, RED2018-102387-T, and RED2018-102471-T), and by the European Commission (ERC-2020-SyG-951281) is gratefully acknowledged.Peer reviewe

Boosting background suppression in the NEXT experiment through Richardson-Lucy deconvolution

Next-generation neutrinoless double beta decay experiments aim for half-life sensitivities of similar to 10(27) yr, requiring suppressing backgrounds to < 1 count/tonne/yr. For this, any extra background rejection handle, beyond excellent energy resolution and the use of extremely radiopure materials, is of utmost importance. The NEXT experiment exploits differences in the spatial ionization patterns of double beta decay and single-electron events to discriminate signal from background. While the former display two Bragg peak dense ionization regions at the opposite ends of the track, the latter typically have only one such feature. Thus, comparing the energies at the track extremes provides an additional rejection tool. The unique combination of the topology-based background discrimination and excellent energy resolution (1% FWHM at the Q-value of the decay) is the distinguishing feature of NEXT. Previous studies demonstrated a topological background rejection factor of 5 when reconstructing electron-positron pairs in the Tl-208 1.6 MeV double escape peak (with Compton events as background), recorded in the NEXT-White demonstrator at the Laboratorio Subterraneo de Canfranc, with 72% signal efficiency. This was recently improved through the use of a deep convolutional neural network to yield a background rejection factor of similar to 10 with 65% signal efficiency. Here, we present a new reconstruction method, based on the Richardson-Lucy deconvolution algorithm, which allows reversing the blurring induced by electron diffusion and electroluminescence light production in the NEXT TPC. The new method yields highly refined 3D images of reconstructed events, and, as a result, significantly improves the topological background discrimination. When applied to real-data 1.6 MeV e(-)e(+) pairs, it leads to a background rejection factor of 27 at 57% signal efficiency.The NEXT Collaboration acknowledges support from the following agencies and institutions: the European Research Council (ERC) under the Advanced Grant 339787-NEXT; the European Union's Framework Programme for Research and Innovation Horizon 2020 (2014-2020) under the Grant Agreements No. 674896, 690575 and 740055; the Ministerio de Economia y Competitividad and the Ministerio de Ciencia, Innovacion y Universidades of Spain under grants FIS2014-53371-C04, RTI2018-095979, the Severo Ochoa Program grants SEV-2014-0398 and CEX2018-000867-S, and the Maria de Maeztu Program MDM-2016-0692; the Generalitat Valenciana under grants PROMETEO/2016/120 and SEJI/2017/011; the Portuguese FCT under project PTDC/FIS-NUC/2525/2014 and under projects UID/04559/2020 to fund the activities of LIBPhys-UC; the U.S. Department of Energy under contracts No. DE-AC02-06CH11357 (Argonne National Laboratory), DE-AC02-07CH11359 (Fermi National Accelerator Laboratory), DE-FG02-13ER42020 (Texas A&M) and DE-SC0019223/DE-SC0019054 (University of Texas at Arlington); the University of Texas at Arlington (U.S.A.); and the Pazy Foundation (Israel) under grants 877040 and 877041. DGD acknowledges Ramon y Cajal program (Spain) under contract number RYC-2015-18820. JM-A acknowledges support from Fundacion Bancaria "la Caixa" (ID 100010434), grant code LCF/BQ/PI19/11690012. AS acknowledges support from the Kreitman School of Advanced Graduate Studies at Ben-Gurion University. Documen

Ba+2 ion trapping using organic submonolayer for ultra-low background neutrinoless double beta detector

If neutrinos are their own antiparticles the otherwise-forbidden nuclear reaction known as neutrinoless double beta decay can occur. The very long lifetime expected for these exceptional events makes its detection a daunting task. In order to conduct an almost background-free experiment, the NEXT collaboration is investigating novel synthetic molecular sensors that may capture the Ba dication produced in the decay of certain Xe isotopes in a high-pressure gas experiment. The use of such molecular detectors immobilized on surfaces must be explored in the ultra-dry environment of a xenon gas chamber. Here, using a combination of highly sensitive surface science techniques in ultra-high vacuum, we demonstrate the possibility of employing the so-called Fluorescent Bicolor Indicator as the molecular component of the sensor. We unravel the ion capture process for these molecular indicators immobilized on a surface and explain the origin of the emission fluorescence shift associated to the ion trapping.This material is based upon work supported by the following agencies and institutions: the European Research Council (ERC) under ERC-2020-SyG 951281; the MCIN/AEI/10.13039/501100011033 of Spain and ERDF A way of making Europe under grants PID2020-114252GB-I00, PID2019-107338RB-C63, PID2019-104772GB-I00, PID2019-111281GB-I00, and RTI2018-095979, the Severo Ochoa Program grant CEX2018-000867-S; the Basque Government (GV/EJ) under grants IT-1553-22, IT-1591-22. The NEXT Collaboration acknowledges support from the following agencies and institutions: the European Union’s Framework Programme for Research and Innovation Horizon 2020 (2014-2020) under Grant Agreement No. 957202-HIDDEN; the MCIN/AEI of Spain and ERDF A way of making Europe under grants RTI2018-095979 and PID2021-125475NB, the Severo Ochoa Program grant CEX2018-000867-S and the Ramón y Cajal program grant RYC-2015-18820; the Generalitat Valenciana of Spain under grants PROMETEO/2021/087 and CIDEGENT/2019/049; the Department of Education of the Basque Government of Spain under the predoctoral training program non-doctoral research personnel; the Portuguese FCT under project UID/FIS/04559/2020 to fund the activities of LIBPhys-UC; the Pazy Foundation (Israel) under grants 877040 and 877041; the US Department of Energy under contracts number DE-AC02-06CH11357 (Argonne National Laboratory), DE-AC02-07CH11359 (Fermi National Accelerator Laboratory), DE-FG02-13ER42020 (Texas A&M), DE-SC0019054 (Texas Arlington) and DE-SC0019223 (Texas Arlington); the US National Science Foundation under award number NSF CHE 2004111; the Robert A Welch Foundation under award number Y-2031-20200401. Finally, we are grateful to the Laboratorio Subterráneo de Canfranc for hosting and supporting the NEXT experiment.Peer reviewe